One measurement channel may transmit modulated radiation (electromagnetic or light) through a medium which may be received after being reflected by a target. Lock-in is then performed on the returned signal. When multiple paths occur (multipath), modulation amplitude variations may result. These variations are due to other reflections of the same channel modulated radiation signal summing in various phases with each other. In these multipath environments, the amplitude variations in the received modulated signal are no longer representative of absorption by the target or medium, thereby resulting in measurement errors.